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/*
* This file is part of the MicroPython project, http://micropython.org/
*
* The MIT License (MIT)
*
* Copyright (c) 2020 Damien P. George
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#ifndef MICROPY_INCLUDED_PY_PAIRHEAP_H
#define MICROPY_INCLUDED_PY_PAIRHEAP_H
// This is an implementation of a pairing heap. It is stable and has deletion
// support. Only the less-than operation needs to be defined on elements.
//
// See original paper for details:
// Michael L. Fredman, Robert Sedjewick, Daniel D. Sleator, and Robert E. Tarjan.
// The Pairing Heap: A New Form of Self-Adjusting Heap.
// Algorithmica 1:111-129, 1986.
// https://www.cs.cmu.edu/~sleator/papers/pairing-heaps.pdf
#include <assert.h>
#include "py/obj.h"
// This struct forms the nodes of the heap and is intended to be extended, by
// placing it first in another struct, to include additional information for the
// element stored in the heap. It includes "base" so it can be a MicroPython
// object allocated on the heap and the GC can automatically trace all nodes by
// following the tree structure.
typedef struct _mp_pairheap_t {
mp_obj_base_t base;
struct _mp_pairheap_t *child;
struct _mp_pairheap_t *child_last;
struct _mp_pairheap_t *next;
} mp_pairheap_t;
// This is the function for the less-than operation on nodes/elements.
typedef int (*mp_pairheap_lt_t)(mp_pairheap_t *, mp_pairheap_t *);
// Core functions.
mp_pairheap_t *mp_pairheap_meld(mp_pairheap_lt_t lt, mp_pairheap_t *heap1, mp_pairheap_t *heap2);
mp_pairheap_t *mp_pairheap_pairing(mp_pairheap_lt_t lt, mp_pairheap_t *child);
mp_pairheap_t *mp_pairheap_delete(mp_pairheap_lt_t lt, mp_pairheap_t *heap, mp_pairheap_t *node);
// Create a new heap.
static inline mp_pairheap_t *mp_pairheap_new(mp_pairheap_lt_t lt) {
(void)lt;
return NULL;
}
// Initialise a single pairing-heap node so it is ready to push on to a heap.
static inline void mp_pairheap_init_node(mp_pairheap_lt_t lt, mp_pairheap_t *node) {
(void)lt;
node->child = NULL;
node->next = NULL;
}
// Test if the heap is empty.
static inline bool mp_pairheap_is_empty(mp_pairheap_lt_t lt, mp_pairheap_t *heap) {
(void)lt;
return heap == NULL;
}
// Peek at the top of the heap. Will return NULL if empty.
static inline mp_pairheap_t *mp_pairheap_peek(mp_pairheap_lt_t lt, mp_pairheap_t *heap) {
(void)lt;
return heap;
}
// Push new node onto existing heap. Returns the new heap.
static inline mp_pairheap_t *mp_pairheap_push(mp_pairheap_lt_t lt, mp_pairheap_t *heap, mp_pairheap_t *node) {
assert(node->child == NULL && node->next == NULL);
return mp_pairheap_meld(lt, node, heap); // node is first to be stable
}
// Pop the top off the heap, which must not be empty. Returns the new heap.
static inline mp_pairheap_t *mp_pairheap_pop(mp_pairheap_lt_t lt, mp_pairheap_t *heap) {
assert(heap->next == NULL);
mp_pairheap_t *child = heap->child;
heap->child = NULL;
return mp_pairheap_pairing(lt, child);
}
#endif // MICROPY_INCLUDED_PY_PAIRHEAP_H
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